Spatial filtering for high power laser beam by volume Bragg grating

Haobin Zheng; Yanlan He; Jichun Tan

doi:10.1117/12.839636

30 November 2009 Spatial filtering for high power laser beam by volume Bragg grating

Haobin Zheng, Yanlan He, Jichun Tan

Proceedings Volume 7506, 2009 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments; 75062A (2009) https://doi.org/10.1117/12.839636
Event: International Conference on Optical Instrumentation and Technology, 2009, Shanghai, China

Abstract

Nowadays, the most widespread used space filters are pinhole filters, consisted of a lens with a pinhole in the focal plane, requiring for matching spatially a focused laser beam to a small hole. Experimentally, the initial alignment of spatial filters is difficult, if the pinhole position changes, a laser can damage the pinhole when the power is increased or even permanent damage due to heating. In contrast, non-spatial filtering, a holographic filter element, which made of volume Bragg grating, is inserted in the laser beam path to selectively diffract light propagating at a particular angle, without a lens or a pinhole. A volume Bragg grating is operated directly on the laser beam propagation angle without focus, made use of the grating's angular selectivity, which alignment is easier than pinhole filter, and endures a high-power laser. In this thesis, a volume Bragg grating was fabricated in a 40μm-thick photopolymer, with period of 911.3nm, preparing for a low-pass non-spatial filtering. It achieves an angular selectivity of 35mrad; diffraction efficiency about 95%. Nevertheless, the results of the experiment can be verified with the theory, but not suitable for high-power application. In that case, the photopolymer's grating should be replaced with a photo-thermo-refractive glass.

Citation Download Citation

Haobin Zheng, Yanlan He, and Jichun Tan "Spatial filtering for high power laser beam by volume Bragg grating", Proc. SPIE 7506, 2009 International Conference on Optical Instruments and Technology: Optical Systems and Modern Optoelectronic Instruments, 75062A (30 November 2009); https://doi.org/10.1117/12.839636

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